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Catweasel mice: a novel role for Six1 in sensory patch development and a model for branchio-oto-renal syndrome.

Bosman EA, Quint E, Fuchs H, Hrabé de Angelis M, Steel KP - Dev. Biol. (2009)

Bottom Line: Bmp4, Jag1 and Sox2 expression were largely absent at early stages of sensory development and NeuroD expression was reduced in the developing vestibulo-acoustic ganglion.Lastly we show that Six1 genetically interacts with Jag1.In addition Six1 has a pivotal role in early sensory patch development and may act in the same genetic pathway as Jag1.

View Article: PubMed Central - PubMed

Affiliation: The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK.

ABSTRACT
Large-scale mouse mutagenesis initiatives have provided new mouse mutants that are useful models of human deafness and vestibular dysfunction. Catweasel is a novel N-ethyl-N-nitrosourea (ENU)-induced mutation. Heterozygous catweasel mutant mice exhibit mild headtossing associated with a posterior crista defect. We mapped the catweasel mutation to a critical region of 13 Mb on chromosome 12 containing the Six1, -4 and -6 genes. We identified a basepair substitution in exon 1 of the Six1 gene that changes a conserved glutamic acid (E) at position 121 to a glycine (G) in the Six1 homeodomain. Cwe/Cwe animals lack Preyer and righting reflexes, display severe headshaking and have severely truncated cochlea and semicircular canals. Cwe/Cwe animals had very few hair cells in the utricle, but their ampullae and cochlea were devoid of any hair cells. Bmp4, Jag1 and Sox2 expression were largely absent at early stages of sensory development and NeuroD expression was reduced in the developing vestibulo-acoustic ganglion. Lastly we show that Six1 genetically interacts with Jag1. We propose that the catweasel phenotype is due to a hypomorphic mutation in Six1 and that catweasel mice are a suitable model for branchio-oto-renal syndrome. In addition Six1 has a pivotal role in early sensory patch development and may act in the same genetic pathway as Jag1.

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The catweasel mutation maps to chromosome 12 and catweasel mice have a mutation in the Six1 gene. (A) Genome scan of 30 Cwe/+ animals. The percentage of animals with two C3H loci is displayed on the Y axis and alternating autosomes in white and grey on the X-axis with each bar representing one marker. (B) Schematical representation of the critical region on chromosome 12 between D12Mit36 and D12Mit274 (61.6–73.6 Mb). The two columns represent the genotypes of two mice with recombination breakpoints that defined the critical region (C) Partial sequencing of genomic DNA of wildtype, Cwe/+ and Cwe/Cwe mice using primers spanning exon 1 of the Six1 gene. Between residue 220 and 230 of the sequenced PCR product, we identified an A to G substitution (red arrow) corresponding to position 411 of the Six1 open reading frame. (D) A schematical representation of the Six1 protein, with its amino-terminal end (red), Six domain (yellow), DNA binding homeobox domain (purple) and putative transactivation domain (green). The amino-terminal region (between residues 87 and 146) of the homeobox domain is conserved between various species. The identified mutation in catweasel mice (red arrow) and residues mutated in branchio-oto-renal syndrome (⁎; Ruf et al., 2004) are indicated. (E–G) Wildtype (E), Cwe/+ (F) and Cwe/Cwe (G) embryos (E9.5) were analysed for Six1 expression by whole mount RNA in situ hybridisation. Six1 is expressed widely with high levels in somites and the otic cup (arrowhead). No significant difference between control and mutant embryos was found. Scale bar = 1 mm. aa, amino acid; ba, branchial arch; dmSine, Drosophila melanogaster Sine oculis; drSix1, Danio rerio Six1; hsSIX1, Homo sapiens SIX1; Mb, mega basepairs; mmSix1-Cwe, Mus musculus Six1 with the catweasel mutation; mmSix1-WT, wildtype Mus musculus Six1; lb, limb bud; so, somites.
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fig2: The catweasel mutation maps to chromosome 12 and catweasel mice have a mutation in the Six1 gene. (A) Genome scan of 30 Cwe/+ animals. The percentage of animals with two C3H loci is displayed on the Y axis and alternating autosomes in white and grey on the X-axis with each bar representing one marker. (B) Schematical representation of the critical region on chromosome 12 between D12Mit36 and D12Mit274 (61.6–73.6 Mb). The two columns represent the genotypes of two mice with recombination breakpoints that defined the critical region (C) Partial sequencing of genomic DNA of wildtype, Cwe/+ and Cwe/Cwe mice using primers spanning exon 1 of the Six1 gene. Between residue 220 and 230 of the sequenced PCR product, we identified an A to G substitution (red arrow) corresponding to position 411 of the Six1 open reading frame. (D) A schematical representation of the Six1 protein, with its amino-terminal end (red), Six domain (yellow), DNA binding homeobox domain (purple) and putative transactivation domain (green). The amino-terminal region (between residues 87 and 146) of the homeobox domain is conserved between various species. The identified mutation in catweasel mice (red arrow) and residues mutated in branchio-oto-renal syndrome (⁎; Ruf et al., 2004) are indicated. (E–G) Wildtype (E), Cwe/+ (F) and Cwe/Cwe (G) embryos (E9.5) were analysed for Six1 expression by whole mount RNA in situ hybridisation. Six1 is expressed widely with high levels in somites and the otic cup (arrowhead). No significant difference between control and mutant embryos was found. Scale bar = 1 mm. aa, amino acid; ba, branchial arch; dmSine, Drosophila melanogaster Sine oculis; drSix1, Danio rerio Six1; hsSIX1, Homo sapiens SIX1; Mb, mega basepairs; mmSix1-Cwe, Mus musculus Six1 with the catweasel mutation; mmSix1-WT, wildtype Mus musculus Six1; lb, limb bud; so, somites.

Mentions: DNA from backcross offspring that exhibited severe headshaking behaviour was used to identify chromosome/trait linkage. Analysis of 57 polymorphic markers distributed throughout the autosomes indicated clear linkage of the catweasel behaviour to chromosome 12 (Fig. 2A). The highest percentage (83.3%) of homozygosity for the C3H-type polymorphism was found at marker D12Mit69. For fine mapping only backcross animals with a confirmed abnormal posterior crista were used (n = 38). This narrowed the interval to the region of chromosome 12 between D12Mit36 and D12Mit274. The haplotypes of the two animals defining this critical region are shown in Fig. 2B. This corresponds to a 13 Mb physical region from 61.6 to 73.6 Mb on chromosome 12.


Catweasel mice: a novel role for Six1 in sensory patch development and a model for branchio-oto-renal syndrome.

Bosman EA, Quint E, Fuchs H, Hrabé de Angelis M, Steel KP - Dev. Biol. (2009)

The catweasel mutation maps to chromosome 12 and catweasel mice have a mutation in the Six1 gene. (A) Genome scan of 30 Cwe/+ animals. The percentage of animals with two C3H loci is displayed on the Y axis and alternating autosomes in white and grey on the X-axis with each bar representing one marker. (B) Schematical representation of the critical region on chromosome 12 between D12Mit36 and D12Mit274 (61.6–73.6 Mb). The two columns represent the genotypes of two mice with recombination breakpoints that defined the critical region (C) Partial sequencing of genomic DNA of wildtype, Cwe/+ and Cwe/Cwe mice using primers spanning exon 1 of the Six1 gene. Between residue 220 and 230 of the sequenced PCR product, we identified an A to G substitution (red arrow) corresponding to position 411 of the Six1 open reading frame. (D) A schematical representation of the Six1 protein, with its amino-terminal end (red), Six domain (yellow), DNA binding homeobox domain (purple) and putative transactivation domain (green). The amino-terminal region (between residues 87 and 146) of the homeobox domain is conserved between various species. The identified mutation in catweasel mice (red arrow) and residues mutated in branchio-oto-renal syndrome (⁎; Ruf et al., 2004) are indicated. (E–G) Wildtype (E), Cwe/+ (F) and Cwe/Cwe (G) embryos (E9.5) were analysed for Six1 expression by whole mount RNA in situ hybridisation. Six1 is expressed widely with high levels in somites and the otic cup (arrowhead). No significant difference between control and mutant embryos was found. Scale bar = 1 mm. aa, amino acid; ba, branchial arch; dmSine, Drosophila melanogaster Sine oculis; drSix1, Danio rerio Six1; hsSIX1, Homo sapiens SIX1; Mb, mega basepairs; mmSix1-Cwe, Mus musculus Six1 with the catweasel mutation; mmSix1-WT, wildtype Mus musculus Six1; lb, limb bud; so, somites.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2682643&req=5

fig2: The catweasel mutation maps to chromosome 12 and catweasel mice have a mutation in the Six1 gene. (A) Genome scan of 30 Cwe/+ animals. The percentage of animals with two C3H loci is displayed on the Y axis and alternating autosomes in white and grey on the X-axis with each bar representing one marker. (B) Schematical representation of the critical region on chromosome 12 between D12Mit36 and D12Mit274 (61.6–73.6 Mb). The two columns represent the genotypes of two mice with recombination breakpoints that defined the critical region (C) Partial sequencing of genomic DNA of wildtype, Cwe/+ and Cwe/Cwe mice using primers spanning exon 1 of the Six1 gene. Between residue 220 and 230 of the sequenced PCR product, we identified an A to G substitution (red arrow) corresponding to position 411 of the Six1 open reading frame. (D) A schematical representation of the Six1 protein, with its amino-terminal end (red), Six domain (yellow), DNA binding homeobox domain (purple) and putative transactivation domain (green). The amino-terminal region (between residues 87 and 146) of the homeobox domain is conserved between various species. The identified mutation in catweasel mice (red arrow) and residues mutated in branchio-oto-renal syndrome (⁎; Ruf et al., 2004) are indicated. (E–G) Wildtype (E), Cwe/+ (F) and Cwe/Cwe (G) embryos (E9.5) were analysed for Six1 expression by whole mount RNA in situ hybridisation. Six1 is expressed widely with high levels in somites and the otic cup (arrowhead). No significant difference between control and mutant embryos was found. Scale bar = 1 mm. aa, amino acid; ba, branchial arch; dmSine, Drosophila melanogaster Sine oculis; drSix1, Danio rerio Six1; hsSIX1, Homo sapiens SIX1; Mb, mega basepairs; mmSix1-Cwe, Mus musculus Six1 with the catweasel mutation; mmSix1-WT, wildtype Mus musculus Six1; lb, limb bud; so, somites.
Mentions: DNA from backcross offspring that exhibited severe headshaking behaviour was used to identify chromosome/trait linkage. Analysis of 57 polymorphic markers distributed throughout the autosomes indicated clear linkage of the catweasel behaviour to chromosome 12 (Fig. 2A). The highest percentage (83.3%) of homozygosity for the C3H-type polymorphism was found at marker D12Mit69. For fine mapping only backcross animals with a confirmed abnormal posterior crista were used (n = 38). This narrowed the interval to the region of chromosome 12 between D12Mit36 and D12Mit274. The haplotypes of the two animals defining this critical region are shown in Fig. 2B. This corresponds to a 13 Mb physical region from 61.6 to 73.6 Mb on chromosome 12.

Bottom Line: Bmp4, Jag1 and Sox2 expression were largely absent at early stages of sensory development and NeuroD expression was reduced in the developing vestibulo-acoustic ganglion.Lastly we show that Six1 genetically interacts with Jag1.In addition Six1 has a pivotal role in early sensory patch development and may act in the same genetic pathway as Jag1.

View Article: PubMed Central - PubMed

Affiliation: The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK.

ABSTRACT
Large-scale mouse mutagenesis initiatives have provided new mouse mutants that are useful models of human deafness and vestibular dysfunction. Catweasel is a novel N-ethyl-N-nitrosourea (ENU)-induced mutation. Heterozygous catweasel mutant mice exhibit mild headtossing associated with a posterior crista defect. We mapped the catweasel mutation to a critical region of 13 Mb on chromosome 12 containing the Six1, -4 and -6 genes. We identified a basepair substitution in exon 1 of the Six1 gene that changes a conserved glutamic acid (E) at position 121 to a glycine (G) in the Six1 homeodomain. Cwe/Cwe animals lack Preyer and righting reflexes, display severe headshaking and have severely truncated cochlea and semicircular canals. Cwe/Cwe animals had very few hair cells in the utricle, but their ampullae and cochlea were devoid of any hair cells. Bmp4, Jag1 and Sox2 expression were largely absent at early stages of sensory development and NeuroD expression was reduced in the developing vestibulo-acoustic ganglion. Lastly we show that Six1 genetically interacts with Jag1. We propose that the catweasel phenotype is due to a hypomorphic mutation in Six1 and that catweasel mice are a suitable model for branchio-oto-renal syndrome. In addition Six1 has a pivotal role in early sensory patch development and may act in the same genetic pathway as Jag1.

Show MeSH
Related in: MedlinePlus